The selective and specific measurement of biological and pharmacological molecules has been enables or significantly enhanced through the use of mass spectrometry. These studies have as a primary goal the development of a true mass spectrometer operating under atomospheric pressure conditions. Removing the requirement for vacuum operating biomedical analysis; with both identify and quantification problems. We intend to demonstrate the ability of a linear quadrupole device to act as a true mass filter. This novel filter is anticipated to detect the entire mass range covered by present mass analyzers in both a scanning mode and the selective ion mode, with the added advantages of no pumps and higher ion transmission efficiency. This device is capable of coupling to any atmospheric pressure ionization technique; particularly electrospray and APCI (atmospheric pressure chemical ionization), the dominant ionization techniques in conventional biomedical mass spectrometry application. We envision that the lack of need for vacuum interface will have as a benefit increased sensitivity as well as diminished cost and complexity from conventional analyzers. PROPOSED COMMERCIAL APPLICATION: We have as specific long-term objectives to couple atmospheric pressure quadrupole devices to the inlet of conventional single mass analyzers (e.g., quadrupole and time-of-flight analyzers) to provide sensitive and affordable MS/MS (mass spectrometry/mass spectrometry) capabilities. We also have as a long-term objective to develop a truly mass specific/selective, and sensitive micro-fabricated device to enable low- cost "out-of-laboratory" mass spectrometric measurements. We also envision this technology enabling very affordable (<$20K) protein analyzers by coupling nanospray with atmospheric pressure analysis.